Blast resistant doors are typically employed in military and industrial facilities where there exists the potential for an explosion and the release of hazardous or noxious materials, such as for example material storage rooms, laboratories, research facilities, ammunition depots, military facilities, and other high security installations. In such facilities, the doors are generally designed in anticipation of a breaching explosion occurring either within the facility, such as would occur from an accidental explosion of the contents of the facility, or outside the facility, such as from an intentionally directed explosive attack by an intruder or terrorist. Various sealing schemes are incorporated to prevent leakage of dangerous materials and gases from occurring in such events. Typically an overlapping arrangement is used, with the blast door designed to close against the side of the facility (i.e. inside or outside) facing the anticipated explosive event. The pressure pulse from an explosive event thus acts in the direction of closing the door, tending to compress the door against the facility and enhance the sealing effect.
However, in some applications there is a need for a blast door capable of maintaining a seal when exposed to explosions or attacks occurring on either side of the door. For example, certain high security installations employ two blast doors to create a Sally Port intended to contain and seal against explosions occurring either within the facility, or within the Sally Port. Similarly, it may be very advantageous for the doors of an ammunition depot to be capable of withstanding an accidental explosion within the facility, as well as a hostile explosive attack from the outside. In such applications the conventional overlapping door arrangement has unavoidable disadvantages from the standpoint of both security and maintaining integrity of the seal.
From the standpoint of maintaining seal integrity, the door overlap is beneficial in one direction, but generally detrimental in the other direction, providing no inherent resistance against pressure applied to the non-overlapping side of the door. In particular, pressure against the non-overlapping side tends to move the door away from the facility wall rather than toward it, thus weakening or releasing the seal.
From a security standpoint, because the pressure pulse is not being transferred to the facility, the entire load is typically carried by the door latching and bolting mechanisms. The resulting loads can produce excessive shear and tensile stresses in these mechanisms and in the fasteners retaining them to the facility structure. Once weakened, they become more vulnerable to further attacks.
Accordingly, a need exists for a sealable, blast resistant door capable of withstanding an explosive pressure load against either side of the door without degradation of the seal. A further need exists for a blast resistant door with a more robust latching and locking design.